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Handle part-word LL/SC in atomic expansion pass #50
Handle part-word LL/SC in atomic expansion pass #50
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Differential Revision: https://reviews.llvm.org/D77213
This cherry-pick resolves an assertion I get when trying to build |
Edit: Oh sorry, you did actually preserve authorship and all. They just didn't keep the commit message the same as the review message, so I thought it was missing. I'll review this in the morning. |
This commit is against the 10.x branch, while Rust still uses 9.x. The patch looks pretty involved though, so might not be easy to backport. |
The commit is technically on upstream master (11.x branch) but applies cleanly to 10.x. But if it's necessary to put it on 9.x, then I'll look into backporting it. |
It's just that rust-lang/rust is still using the 9.x branch, so if you want this to be useful soon, it will have to be applied there. We'll switch to the 10.x branch once we've satisfied the current performance concerns (or we decide to eat that loss). |
Sure, makes sense. Can we consider merging it to 10.x anyways? Even if it goes into 9.x I'll need it on 10.x branch for when rust upgrades. It looks like it may not be too hard to backport to 9.x, in progress now. |
Created PR #51 -- is that the right 9.x branch? |
50: Extend the .llvm_bb_addr_map section with PT decoding hints. r=ltratt a=vext01 Co-authored-by: Edd Barrett <vext01@gmail.com>
…callback The `TypeSystemMap::m_mutex` guards against concurrent modifications of members of `TypeSystemMap`. In particular, `m_map`. `TypeSystemMap::ForEach` iterates through the entire `m_map` calling a user-specified callback for each entry. This is all done while `m_mutex` is locked. However, there's nothing that guarantees that the callback itself won't call back into `TypeSystemMap` APIs on the same thread. This lead to double-locking `m_mutex`, which is undefined behaviour. We've seen this cause a deadlock in the swift plugin with following backtrace: ``` int main() { std::unique_ptr<int> up = std::make_unique<int>(5); volatile int val = *up; return val; } clang++ -std=c++2a -g -O1 main.cpp ./bin/lldb -o “br se -p return” -o run -o “v *up” -o “expr *up” -b ``` ``` frame rust-lang#4: std::lock_guard<std::mutex>::lock_guard frame rust-lang#5: lldb_private::TypeSystemMap::GetTypeSystemForLanguage <<<< Lock rust-lang#2 frame rust-lang#6: lldb_private::TypeSystemMap::GetTypeSystemForLanguage frame rust-lang#7: lldb_private::Target::GetScratchTypeSystemForLanguage ... frame rust-lang#26: lldb_private::SwiftASTContext::LoadLibraryUsingPaths frame rust-lang#27: lldb_private::SwiftASTContext::LoadModule frame rust-lang#30: swift::ModuleDecl::collectLinkLibraries frame rust-lang#31: lldb_private::SwiftASTContext::LoadModule frame rust-lang#34: lldb_private::SwiftASTContext::GetCompileUnitImportsImpl frame rust-lang#35: lldb_private::SwiftASTContext::PerformCompileUnitImports frame rust-lang#36: lldb_private::TypeSystemSwiftTypeRefForExpressions::GetSwiftASTContext frame rust-lang#37: lldb_private::TypeSystemSwiftTypeRefForExpressions::GetPersistentExpressionState frame rust-lang#38: lldb_private::Target::GetPersistentSymbol frame rust-lang#41: lldb_private::TypeSystemMap::ForEach <<<< Lock #1 frame rust-lang#42: lldb_private::Target::GetPersistentSymbol frame rust-lang#43: lldb_private::IRExecutionUnit::FindInUserDefinedSymbols frame rust-lang#44: lldb_private::IRExecutionUnit::FindSymbol frame rust-lang#45: lldb_private::IRExecutionUnit::MemoryManager::GetSymbolAddressAndPresence frame rust-lang#46: lldb_private::IRExecutionUnit::MemoryManager::findSymbol frame rust-lang#47: non-virtual thunk to lldb_private::IRExecutionUnit::MemoryManager::findSymbol frame rust-lang#48: llvm::LinkingSymbolResolver::findSymbol frame rust-lang#49: llvm::LegacyJITSymbolResolver::lookup frame rust-lang#50: llvm::RuntimeDyldImpl::resolveExternalSymbols frame rust-lang#51: llvm::RuntimeDyldImpl::resolveRelocations frame rust-lang#52: llvm::MCJIT::finalizeLoadedModules frame rust-lang#53: llvm::MCJIT::finalizeObject frame rust-lang#54: lldb_private::IRExecutionUnit::ReportAllocations frame rust-lang#55: lldb_private::IRExecutionUnit::GetRunnableInfo frame rust-lang#56: lldb_private::ClangExpressionParser::PrepareForExecution frame rust-lang#57: lldb_private::ClangUserExpression::TryParse frame rust-lang#58: lldb_private::ClangUserExpression::Parse ``` Our solution is to simply iterate over a local copy of `m_map`. **Testing** * Confirmed on manual reproducer (would reproduce 100% of the time before the patch) Differential Revision: https://reviews.llvm.org/D149949
Differential Revision: https://reviews.llvm.org/D77213